The present invention relates to a magnetic bearing device with a magnet device which is designed to be annular and which has a central axis, for retaining a shaft on the central axis in a rotatable manner by means of magnetic forces.
In conventional, radial magnetic bearings having no permanent magnetic bias, the use of an AC winding to generate a stationary magnetic bias is known. Reference is made here by way of example to the publication DE 23 58 527 A1. The active magnetic bearing presented therein is equipped with a rotary drive comprising stator and rotor with an air gap that is monitored by sensors. A rotating field that is generated by stator windings through the application of alternating current is overlaid with a control field that is generated by windings in the stator through the output currents of amplifiers.
The publication EP 2 148 104 A1 further discloses a magnetic radial bearing having electromagnets disposed in a distributed arrangement in the circumferential direction. The electromagnets each have a common coil for the generation of a magnetic bias and a magnetic, multi-phase rotating field. First and second halves of the coils are each interconnected in a star point. Both star points are provided for connection to a DC power supply for the production of a magnetic bias. The remaining coil ends are provided for parallel connection to a corresponding multi-phase AC controller for the production of a rotating field.
Magnetic bearings serve to bear rotatable shafts. They must also compensate for the gravitational force that acts statically on the shaft. In addition they must also be able to compensate for other specifiable forces, such as e.g. forces generated by imbalances. In order to compensate for these specifiable forces and simultaneously also to center the shaft, the control or regulation element of the magnetic bearing and the coils of the magnetic bearing must have a suitable design.
The publication DE 23 42 767 A1 discloses a generic magnetic bearing device. Here for example an electromagnet is accommodated in a pan-shaped permanent magnet, and the two work together with another permanent magnet suspended above.
The publication WO 95/20260 A1 shows an induction machine with a special winding for the combined generation of a torque and a shear force in same. A similar electric machine with a magnetically mounted rotor is known from the publication DE 91 12 183 U1.
The publication U.S. Pat. No. 3,791,704 A further shows a magnetic bearing in which the permanent magnets are adjustably positioned by means of a screw.